The present invention relates to an apparatus for generating numerical control information which is supplied with data on the shape of a workpiece for each machining step and which generates the numerical control information based on these shape data.
FIG. 1 is a block diagram of an example of a conventional numerical control information generating apparatus. In this configuration, before-machining shape data SA which provides information on a shape for a work piece before the machining, after-machining shape data SB which provides information on a shape for a work piece after the machining, and step tool data SC which provides information on a tool to be used for each machining process, all of which are inputted from a data input unit 1, are stored, after possing through a data input section 2, in a before-machining shape storing section 3, an after-machining shape storing section 7 and a step tool data storing section 6, respectively. The before-machining shape data SA is read out of the before-machining shape storing section 3 into a before-machining shape dividing section 4, and divided into before-step-machining shape data SD, which indicate the data on the shape before the machining for each machining step, to be stored in a before-step-machining shape storing section 5. The after-machining shape data SB is read out of the after-machining shape storing section 7 to an after-machining shape dividing section 8, and divided into after-step-machining shape data SE, which indicates the data after the machining for each machining step, to be stored in an after-step-machining shape storing section 9.
In a display control section 12, the before-machining shape data SA, the after-machining shape data SB, the before-step-machining shape data SD, the after-step-machining shape data SE and the step tool data SC are respectively read out of the before-machining shape storing section 3, the before-step-machining shape storing section 5, the after-machining shape storing section 7, the after-step-machining shape storing section 9 and the step tool data storing section 6. The data is displayed on a display unit 14 via a display data output section 13 by selecting display data SF.
On the other hand, when the before-step-machining shape data SD, the after-step-machining shape data SE and the step tool data SC are respectively read out of the before-step-machining shape storing section 5, the after-step-machining shape storing section 9 and the step tool data storing section 6 into a numerical control information generating section 10, a numerical control information SG is generated and outputted via the numerical control information output section 11 through a medium such as a paper tape 15, a magnetic disc 16 or a communication signal 17.
In the configuration described above, if a before-machining shape data "PPxPcPyP" and an after-machining shape data "PPxP.sub.A P.sub.B P.sub.Y P" as shown in FIG. 2 are inputted, a required machining process for treating the machining region "P.sub.A PcP.sub.B P.sub.A " indicated in the hatched portion in the figure as the difference between the shape at the time of completion of the machining and the shape before the machining, are generated from the combination of the step tool data and the after-machining shape "P.sub.A P.sub.B " of the machining region. For example, in the case where the aforementioned machining process is carried out by a forward longitudinal direction rough outside diameter machining (to be abbreviated as rough outside machining (.rarw.) hereinafter and the arrow denotes the direction corresponding to the figure), the machining start point "Po" and the machining end point "P.sub.5 " for the after-rough-outside-machining (.rarw.) shape are, as shown in FIG. 3, determined based on the after-machining shape "P.sub.A P.sub.B " in the machining region. Subsequently, an after-step-machining shape data in accordance with the machining direction of the rough outside machining (.rarw.) is formed in the order of "Po.fwdarw.P.sub.1 .fwdarw. . . . .fwdarw.P.sub.5 ". Consequently, the forward direction cutting tool moves machining in the negative direction of the Z-axis while cutting in the work piece in the negative direction along the X-axis. It is noted in the figure that the forward direction tool rapidly traverses in the part of the dashed line while effecting cutting traverse in the part of the solid line.
In the case of processing the machining region "P.sub.A P.sub.C P.sub.B P.sub.A " of the shape before the machining as shown in FIG. 2, the above mentioned rough outside machining (.rarw.) can carry out a machining with a sufficient precision. On the other hand, if the thickness W in the direction of the Z-axis is small in the shape at the time of completion of the machining, it may happen that the rough outside machining (.rarw.) can not perform the machining with a necessary quality. In such a case, instead of the rough outside machining (.rarw.), an end face machining (to be referred as to a rough outside end machining (.dwnarw.) is to be applied so as to change the machining direction to the X-axis negative direction. In connection with this change, it is necessary to regenerate an after-step-machining shape data in accordance with the machining direction of the rough outside end machining (.dwnarw.). In the conventional numerical control information generating apparatus described above, however, even when the step types of the machining process are changed in the previously stored machining process, a new after-step-machining shape data is not generated in accordance with the cutting direction of the changed machining process. The above detailed numerical control information generating apparatus, however has had a defect that in some cases the after-step-machining shape data are unchanged, remaining associated with the cutting direction of the previously stored machining process, or otherwise, all of that previously stored data is deleted. Accordingly, an operator has had to re-input new after-step-machining shape data relating to the cutting direction of the changed machining process and this has imposed a heavy burden on the operator.